In this example, this means you are trying to preload a script called
/perl/test.pl, located at
/home/httpd/perl/test.pl in the filesystem. This
error shows up when Apache::RegistryLoader fails
to translate the URI into the corresponding filesystem path. Most
failures happen when a user passes a file path (such as
/home/httpd/perl/test.pl) instead of a relative
URI (such as /perl/test.pl).

You should either provide both the URI and the filename:

Apache::RegistryLoader->new->handler($uri, $filename);

or supply a callback subroutine that will perform the URI-to-filename
conversion. The callback accepts the URI as an argument and returns a
filename. For example, if your mod_perl scripts reside in
/home/httpd/perl-scripts/ but the base URI is
/perl/, you might do the following:

Here, we initialize the Apache::RegistryLoader
object with the uri2filename( ) function that will
perform the URI-to-filename translation. In this function, we just
adjust the URI and return the filename based on the location of the
server root. So if the server root is
/home/httpd/, the callback will return
/home/httpd/perl-scripts/test.pl—exactly
what we have requested.

For more information please refer to the
Apache::RegistryLoader manpage.